Charlatans of the world unite. A conjurer (Welles) attracts a street crowd as he changes keys into coins and produces a fluffy, white rabbit. A girl (Oja Kodar) walks down the street in an eye-catching miniskirt. Gentlemen gawkers duly gawp, unaware that cameras are trained on their turning heads. “Look at them acting away as if they were in a movie,” chuckles Welles. “Grand larceny!”

The author envisaged F for Fake as a new kind of film, a celluloid curio comprising interviews, archive footage, candid photography, and tangents. All the while, our amiable, velvet-voiced narrator and guide rehearses arguments pertaining to truth and fiction. reality and art. He makes for Ibiza, “an island in the sun where lost souls can find one another”, to visit with art forger Elmyr de Hory and de Hory’s similarly fanciful biographer, Clifford Irving. Welles swoons over Chartres, marvelling at the French cathedral’s “rich stone forest” and its potentially post-human testament “to what we had in us”. It’s a monologue many critics regard as the most profound in all cinema in a film that loudly broadcasts its association with bullshit and bullshitters.

F for Fake trades on such screwy dialectics. Welles, an accomplished magician in real life, harks back to early Soviet film practitioners with a view of cinema that forms a nexus between art and science. His predecessors duly stacked one conflicting image on top of another so that the flow of celluloid was consistently counterpointed by the shock of juxtaposition. No picture since Eisenstein’s death exemplifies the escalating power of montage quite like Orson Welles’s swansong, and no picture raises the curtain on the methodology quite so high.

Mostly, though, it’s mad stuff altogether. “In case . . . it seem(s) like there’s going to be some trickery in this film about trickery, we’ll repeat our promise again in writing: for the next hour everything in this film is based strictly on the available facts.” Oh, Orson Welles, sir: you do go on. The one-time perpetrator of an invasion hoax and the wunderkind behind Citizen Kane had spiralled out of fashion and out of Hollywood by the time he came to make F for Fake in 1974. The film was his last completed venture in a career marred by shaky finances and unfinished projects. F for Fake places its creator centre stage as a dazzling showman and an incorrigible prankster. The film is haphazard and wilfully postmodern, but it’s exactly where Welles ought to be.